actually after thinking about it, the 2 larger fish came from the same aquarium, which were given to me by the shop because they sold me a pair of super eruptions, the female had lateral line, which was barely visible i rang them explained to them that it had that and they had sold me a diseased fish, after it died and a few emails they reimbursed me the money that the female was worth only to use at there shops.

I brought a white diamond and red melon, they actually havent grown and both now have lateral. This is after like 8 months. When other discus i have had grow far bigger then them that were the same size when i got.

i wonder if the fish from that shop have brought this disease to my tanks?